1. Field of the Invention
The present invention relates to liquid crystal display devices that each includes a backlight using light-emitting diodes (LEDs) as a light source, the liquid crystal display devices incorporating a preventive measure against color unevenness in the vicinity of the light source.
2. Description of the Related Art
Liquid crystal display devices include a thin-film transistor (TFT) substrate formed by elements such as pixel electrodes and TFTs, a counter substrate facing the TFT substrate, and liquid crystals sandwiched between the TFT substrate and the counter substrate. The transmittance of the light passing through the liquid crystal molecules is controlled on a pixel-by-pixel basis to form an image.
Since the liquid crystals themselves do not emit light, a backlight is disposed on a rear side of a liquid crystal display panel. Each of the liquid crystal display devices such as cellular phones uses LEDs as a light source for the backlight. The LEDs are arranged on a side surface of a light guide plate, various optical sheets are also arranged on the light guide plate, and these optical parts are accommodated in a molding, thereby to configure the backlight. The method of arranging the LEDs on the side surface of the light guide plate is called the side light method.
The LEDs constitute a point light source, and the uniformity of luminance in the backlight therefore is a vital factor. JP-A-2013-69498 describes a configuration intended to obtain uniform luminance of a backlight by forming linear prismatic grooves on a lower surface of a light guide plate. JP-A-2013-93199 describes configurations of two kinds of grooved structures. One of the grooves structures is disposed on at least one of a light-emitting surface and a counter surface of a light guide plate. The other one having anisotropic diffusion characteristics is on the light-receiving surface. These grooved structures enable uniform luminance of light from a backlight.